Biology: Choose a topic

Write a topic and replay for other 2 students posts.
Please post in minimum 500 words about your topic. Aspects to cover will depend on your topic, but here are some suggestions:If a disease, what is its cause, how does it manifests, prevalence, risk factors, prevention, treatment etc.
If a type of organism, what is its classification, characteristics, habitat, its role in the ecosystem, any human use (or abuse), importance etc.
If a substance, what is its chemical nature, where is it obtained from (or how is it made), how does it act, its relevance, use etc.
If a procedure, what is it based upon? What is it used for, what is its relevance?

Provide 2 peer-reviewed references or reputable websites. See the CRAAP test
Attach/insert one picture/diagram illustrating your topic.